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18 Dec 2019

An experiment was to identify the unknown solution as sodium carbonate or sodium bicarbonate by reacting it with HCl and taking pressure measurements. My chemical equations are: NaHCO3+HCl--->CO2+H2O+NaCl Na2CO3+2HCl--->CO2+H2O+2NaCl. The instructor said that it can be determined by looking at the chemical equation. My response was the pressure measurements were from the unknown were closer to sodium bicarbonate than sodium carbonate. Is this a correct assumption?

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Bunny Greenfelder
Bunny GreenfelderLv2
31 Dec 2019

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Related questions

A.Assuming you weighed out a 2.3684 g sample of your unknown, and dissolved and diluted it as in the procedure below, and it took 35.63 mL of a 0.1025 M HCl titrant to reach the endpoint, what are the weight percents of Na2CO3 and NaHCO3 in your unknown sample? Solve the simultaneous equations similar to what we did in Ch 27.

Hints:

-Set g Na2CO3 = X

-Eqn A: bicarbonate + carbonate = diluted weighted mass (remember, the mass is not 2.3684, you diluted it before you titrated it. Calculate the diluted g of unknown)

-Convert the g of Na2CO3 to mol of HCl

-Convert the g of NaHCO3 to mol of HCl

-mol HCl = mol HCl from Na2CO3 + mol HCl from NaHCO3

-Before taking the final weight percent, undo the dilution to get back to the original wt % in the unknown

-Na2CO3 + 2HCl ↔ 2 NaCl + H2O + CO2

-NaHCO3 + HCl ↔ NaCl + H2O + CO2


If a student attempts to identify an unknown compound by methodused in this experiment. She finds that when she heated a sampleweighing 0.4862 g the mass went down appreciably, to 0.3067 g. Whenthe product was converted to chloride, the mass went up, to0.3380g.

a. Is the sample a carbonate? Give your reasoning.
b. What are the two compounds that might be the unknown?
c. Write the chemical equation for the overall reaction that wouldoccur when the original compound was converted to a chloride. Ifthe compound is a hydrogen carbonate, use the sum of Reactions 1and 2. If the sample is carbonate, use Reaction 2.Write theequation for a sodium salt and the for a potassium salt.

Reaction 1:
2 NaHCO3 (s) -> Na2CO3 (s) + H2O (l) + CO2 (g)

Reaction 2:
KHCO3 (s) + HCl (aq) -> KCl (s) + H2O (l) +CO2 (g)

d. How many moles of the chloride salt would be produced from onemole of the original compound?
e. How many grams of the chloride salt would be produced from onemolar mass of the original compound?

Molar masses: NaHCO3 _______g Na2CO3 _______g NaCl_______g
KHCO3 _______g K2CO3 _______g KCl_______g

If a sodium salt, _______g original compound -> _______gchloride
If a potassium salt, _______g original compound -> _______gchloride

f. What is the theoretical value of Q,

If she has an Na salt? _______ if she has a K salt? _______

g. What was the observe value of Q?
h. Which compound did she have an unknown?

IDENTIFICATION OF A COMPOUND BY MASS RELATIONSHIPS

If a student attempts to identify an unknown compound by methodusedin this experiment. She finds that when she heated a sampleweighing0.5015 g the mass went down appreciably, to 0.3432 g. Whentheproduct was converted to chloride, the mass went up, to0.3726g.

a. Is the sample a carbonate? Giveyourreasoning.
b. What are the two compounds that might betheunknown?
c. Write the chemical equation for theoverallreaction that would occur when the original compound wasconvertedto a chloride. If the compound is a hydrogen carbonate,use the sumof Reactions 1 and 2. If the sample is carbonate, useReaction 2.Write the equation for a sodium salt and the for apotassiumsalt.

Reaction 1:
2 NaHCO3 (s) -> Na2CO3 (s) +H2O (l) + CO2 (g)

Reaction 2:
Na2CO3 (s) + 2H+ (aq)+ 2 Cl- (aq) -> 2 NaCl (s) +H2O (l) +CO2 (g)

d. How many moles of the chloride salt wouldbeproduce from one mole of the original compound?
e. How many grams of the chloride salt wouldbeproduced from one molar mass of the original compound?

Molar masses: NaHCO3_______g Na2CO3_______g NaCl_______g
KHCO3_______g K2CO3_______g KCl_______g

If a sodium salt,_______goriginal compound -> _______g chloride
If a potassium salt, _______g original compound ->_______gchloride

f. What is the theoretical value of Q,

If she has an Na salt? _______ if she has a K salt? _______

g. What was the observe value of Q?
h. Which compound did she have anunknown?


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